Delta Air Lines is buying a refinery in a novel — and some say risky — attempt to slice $300 million a year from its escalating jet fuel bill.

The airline said Monday that it is buying the refinery near Philadelphia for $150 million from Phillips 66, a refining company being spun off from ConocoPhillips. The refinery has struggled to make money, and ConocoPhillips planned to shut it down if it couldn’t find a buyer.

Fuel is the largest and most volatile expense for the major airlines. They paid an average of $2.86 a gallon for jet fuel last year, up from $2.09 in 2007, according to statistics from the Bureau of Transportation.